Insulation containing a layer of textile, rotary and/or flame attenuated fibers, and process for producing the same

ABSTRACT

An insulation product contains a layer of textile, rotary and/or flame attenuated fibers. A process for manufacturing the insulation product includes passing fibrous bundles of one or more of textile fibers and of rotary and/or flame attenuated fibers together through an apparatus that separates the fibers and the mixes the separated fibers. The bundles of rotary and/or flame attenuated fibers can be in the form of specially manufactured mats and/or can be production scraps. The resulting mixture of fibers is formed into a non-woven batt, mat, blanket, or board. The process provides homogeneous fiber product with an improved appearance. The textile fibers can enhance thickness recovery of compressed product. Blends of textile glass fiber with rotary and/or flame attenuated glass fiber exhibit an improved combination of thermal and acoustic insulating performance and adequate strength, at a low production cost.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to fiber insulation. More specifically, thisinvention relates to thermal and acoustic insulation containing a layerof textile, rotary and/or flame attenuated fibers. This invention alsorelates to processes for manufacturing the fiber insulation.

2. Description of the Background

Glass and polymer fiber mats positioned in the gap between two surfacescan be used to reduce the passage of heat and noise between thesurfaces.

Heat passes between surfaces by conduction, convection and radiation.Because glass and polymer fibers are relatively low thermal conductivitymaterials, thermal conduction along glass and polymer fibers is minimal.Because the fibers slow or stop the circulation of air, mats of thefibers reduce thermal convection. Because fiber mats shield surfacesfrom direct radiation emanating from other surfaces, the fiber matsreduce radiative heat transfer. By reducing the conduction, convectionand radiation of heat between surfaces, fiber mats provide thermalinsulation.

Sound passes between surfaces as wave-like pressure variations in air.Because fibers scatter sound waves and cause partial destructiveinterference of the waves, a fiber mat attenuates noise passing betweensurfaces and provides acoustic insulation.

Conventional fiber mats or webs used for thermal and acoustic insulationare made either primarily from textile fibers, or from rotary or flameattenuated fibers. Textile fibers used in thermal and acousticinsulation are typically chopped into segments 2 to 15 cm long and havediameters of greater than 5 μm up to 16 μm. Rotary fibers and flameattenuated fibers are relatively short, with lengths on the order of 1to 5 cm, and relatively fine, with diameters of 2 μm to 5 μm. Mats madefrom textile fibers tend to be stronger and less dusty than those madefrom rotary fibers or flame attenuated fibers, but are somewhat inferiorin insulating properties. Mats made from rotary or flame attenuatedfibers tend to have better thermal and acoustic insulation propertiesthan those made from textile fibers, but are inferior in strength.

Conventional fiber insulation often contains a non-uniform fiberdistribution and fails to provide a satisfactory combination ofinsulation and strength. Conventional fiber insulation also tends to beexpensive. Especially in ductliner applications, a need exists for new,low cost, uniform fiber products with an improved combination ofinsulation, strength and handling characteristics. Processes to producethese products are also needed.

SUMMARY OF THE INVENTION

The present invention provides a fiber insulation product including alayer of textile, rotary and/or flame attenuated fibers. A mixture oftextile and of rotary and/or flame attenuated fibers results in a lowcost insulation product with superior thermal and acoustic insulationproperties. The mixed layer can be formed by combining textile fibersand rotary and/or flame attenuated fibers, chopping the combined fiberstogether to mix and shorten the fibers, and then forming a mat from themixed fibers. An insulation product of 100% textile glass fibers that isformed by a state of the art air-laid process exhibits better uniformitythan conventional textile glass products.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention will be described in detail,with reference to the following figure, wherein:

FIG. 1 shows a process for manufacturing an insulation product includinga mixed layer of textile glass fibers and of rotary and/or flameattenuated glass fibers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In embodiments, the fiber insulation product of the present inventionincludes a mixed layer of textile fibers and of rotary and/or flameattenuated fibers. In other embodiments, the fiber insulation product ofthe present invention can be either 100% textile fibers or 100% rotaryand/or flame attenuated fibers.

The fibers in the insulation product can form a nonwoven porousstructure. The nonwoven fibers can be in the form of a batt, mat,blanket or board. In the mixed layer, the textile fibers and the rotaryand/or flame attenuated fibers intermingle. Preferably, the mixed layeris a uniform mixture of the textile fibers and of the rotary and/orflame attenuated fibers. When the insulation product is 100% textilefibers or 100% rotary and/or flame attenuated fibers, preferably thefibers are uniformly distributed in the insulation product in order tooffer a constant quality.

The fibers can be organic or inorganic, and natural or man-made.Suitable organic fibers include cellulosic polymer fibers, such asrayon; and thermoplastic polymer fibers, such as polyester or nylon.Natural fibers include cotton, silk, flax and wool. Preferably, thefibers are inorganic. Inorganic fibers include rock wool and glass wool.

Preferably, the fibers are inorganic and comprise a glass. The glass canbe, for example, an E-glass, a C-glass, or a high boron content C-glass.

In embodiments, each of the fibers can be made of the same material. Inother embodiments with a mixed fiber layer, the textile fibers can bemade from one material, and the rotary and/or flame attenuated fiberscan be made from a different material. In still other embodiments,different textile fibers can each be made from different materials;and/or different rotary or flame attenuated glass fibers can be madefrom different materials. Cost and insulation requirements will dictatethe selection of the particular materials used in the textile, rotaryand flame attenuated fibers. Preferably, the textile fibers are formedfrom starch coated or plastic coated E-glass. Preferably, the rotary andflame attenuated fibers are formed from high boron C-glass.

Man-made textile, rotary and flame attenuated fibers can be made invarious ways known in the art. For example, textile fibers can be formedin continuous processes in which molten glass or polymer is extruded anddrawn from apertures to lengths on the order of one mile. For use ininsulation, the long textile fibers are divided into short segments bycutting techniques known in the art. Rotary fibers can be made or spunby using centrifugal force to extrude molten glass or polymer throughsmall openings in the sidewall of a rotating spinner. Flame attenuatedfibers can be formed by extruding molten glass or polymer from aperturesand then blowing the extruded strands at right angles with a highvelocity gas burner to remelt and reform the extruded material as smallfibers.

The textile fibers used in the insulation product of the presentinvention have diameters of from greater than 5 μm to about 16 μm.Preferably the textile fibers are divided into segments with lengths ofabout 2 cm to about 15 cm, more preferably from about 6 cm to about 14cm. The rotary and flame attenuated fibers have diameters of from about2 μm to 5 μm. Preferably the rotary and flame attenuated fibers havelengths of about 1 cm to about 5 cm, more preferably from about 2 cm toabout 4 cm.

The insulation product according to the present invention can bemanufactured in a variety of ways. For example, the mixed layer can beformed by dividing long textile fibers into textile fiber segments,mixing the textile fiber segments with rotary and/or flame attenuatedfibers, and depositing the collection of mixed fibers and fiber segmentson a surface in a sheet former. Insulation product containing 100%textile fibers or 100% rotary and/or flame attenuated fibers can besimilarly formed by dividing fibers into fiber segments and depositingthe collection of fiber segments on a surface in a sheet former. Thesurface of the sheet former can be stationary or moving. Preferably, thesurface is provided by a perforated rotating drum, or by a movingconveyor or forming belt. The textile fibers can be divided in variousways known in the art, such as chopping or combing textile fibers.

A binder can be used to capture and hold the fibers in the insulationproduct together. The binder can be organic or inorganic. The binder canbe a thermosetting polymer, a thermoplastic polymer, or a combination ofboth thermoplastic and thermosetting-polymers. Preferably, thethermosetting polymer is a phenolic resin, such as a phenol-formaldehyderesin, which will cure or set upon heating. The thermoplastic polymerwill soften or flow upon heating above a temperature such as the meltingpoint of the polymer. The heated binder will join and bond the fibers.Upon cooling and hardening, the binder will hold the fibers together.When binder is used in the insulation product, the amount of binder canbe from 1 to 30 wt %, preferably from 3 to 25 wt %, more preferably from4 to 24 wt %. The binder can be added to and mixed with the fiberspreferably before but also possibly after the processes described above.

In the case of blended textile fibers and rotary and/or flame attenuatedfibers, a particularly efficient means of forming the mixed layerinvolves passing pre-opened fiber nodules of textile fibers and afibrous mat of rotary and/or flame attenuated fibers together through anapparatus configured to divide the fibers. The fibrous materials caneach be either woven or non-woven, but are preferably non-woven. Thefibrous mats of rotary and/or flame attenuated fibers can be speciallymanufactured and/or can include shredded production scrap. Inembodiments, only the textile fibers are divided in the fiber dividingapparatus. In other embodiments, both the textile fibers and the rotaryand/or flame attenuated fibers are divided in the fiber dividingapparatus. An example of a fiber dividing apparatus is a tearingdistribution system in which fibers are tom into fiber segments betweeninterdigitated bars. Another example of such an apparatus is thecombination of the above apparatus for rotary mat tearing and a cuttingsystem in which textile fiber is cut by knives into fiber segments.Still another such apparatus is a sucking or depression forming hood.Divided textile and rotary and/or flame attenuated fibers passingthrough the apparatus are deposited onto a surface to form a mixed layerof textile fiber segments and of rotary and/or flame attenuated fibers.Preferably, the surface is provided by a moving rotating perforateddrum, or conveyor or forming belt. The mixed layer can be in the form ofa fibrous batt, mat, blanket, or board.

A preferred method of forming the insulation products of 100% textilefibers or of 100% rotary or flame attenuated fibers or of blended fibersis by an air-laid process using a machine sold by DOA (Dr. OttoAngleitner Ges.m.b.H. & Co. KG, A-4600 Wels, Daffingerstasse 10,Austria). In this process every fiber component is finely andindividually opened and separated, weighed, and then blended at adesired ratio in a collection of fibers through a pneumatictransportation system to a fiber condenser. From the condenser, thefiber collection is weighed, and then passed through at least one sievedrum sheet former. To supply a binder, a powder binder strewer andweighing device are installed before the last sheet former. Theresulting homogenous blend of fibers and binder can have less than 10 wt%, preferably less than 5 wt %, more preferably less than 3 wt %dispersion, based on 0.5 m² sample surface.

Preferably the relative humidity is 40% or greater, more preferably 50%or greater, in the sheet formers when forming the insulation product byan air-laid process such as that using the DOA machine. If the relativehumidity is less than 40%, static electricity causes fibers to repel oneanother, which makes it extremely difficult if not impossible to produceinsulation product having homogeneous and uniform fiber dispersions. Thestatic electricity produced in the air-laid process when the relativehumidity is less that 40% is surprising, because one would not haveexpected that under these conditions the friction between fibers and thesieve drum sheet former would have been intense enough to produce thestatic electricity. This surprising and potentially fatal effect can beovercome or reduced by adding an antistatic agent to the fiber, e.g., byspraying water in with the fiber, by adding an antistatic chemical tothe fiber, or by an appropriate selection of binder. After theinsulation product is produced in a humid or less static environment,excess water can be removed by heating, e.g., when the binder is cured.

In embodiments, the thickness of the fiber layer of the insulationproduct of the present invention is preferably in a range from 4 to 250mm, more preferably from 10 to 205 mm, most preferably from 12 to 76 mm.When the insulation product contains the mixed fiber layer, thepercentage of textile fiber in the product can be in a range of 1 to99%, preferably from 20% to 70% and more preferably from 25% to 50%. Thehigher the percentage of textile fiber, the stronger the product.However, higher percentages of textile fiber lead to a reduction inacoustic and thermal insulation performance with high cost.

Insulation product produced by a state of the art air-laid process,especially on a DOA machine, exhibits a consistent surface appearanceand smoothness, a homogeneous color, and, more surprisingly, a structureof inclined overlaid fiber layers, in particular with 100% textilefiber. This special oriented structure is beneficial for thicknessrecovery after long storage of the insulation under compression atthicknesses 25% of the nominal thickness or less.

EXAMPLE

The following non-limiting example will further illustrate theinvention.

FIG. 1 illustrates various embodiments of the invention. A bale oftextile glass fibers and a bale of rotary glass fibers are opened byrespective bale openers (not shown). Opened textile glass fibers 1 andopened rotary glass fibers 2 at a desired ratio are conveyed and mixedinto a column feed 3. A first sheet former 4 again mixes the fibers, anda binder powder 5 is then added to the combined rotary and textilefibers. The textile fibers 1, rotary fibers 2, and binder powder 5 thenenter a second sheet former 6 where the textile and the rotary glassfibers are mixed together with the binder to form a mixture of fibersand binder. The mixture of fibers and binder form a uniformrotary/textile fiber primary mat at the outlet of the second sheetformer 6. When the primary mat passes through curing oven 7, the binderpowder 5 flows to fix the fibers and form the finished insulationproduct 8. In embodiments, the rotary glass fibers 2 are not added tothe textile glass fibers 1, which results in an insulation product thatis 100% textile glass fiber. In other embodiment, the textile glassfibers 1 are not added to the rotary glass fibers 2, which results in aninsulation production that is 100% rotary glass fiber. It should beunderstood from the above description that more than one kind of fiber(e.g., inorganic, organic, natural fibers) can be used in the process ata desired ratio in a similar way.

Table 1 compares tested R-values (index of thermal insulation) andNRC-values (noise reduction coefficient) for a layer made of onlytextile fibers and a uniform layer of rotary (30%) and textile (70%)fibers. The textile fibers are made from E-glass and the rotary are madefrom C-glass. TABLE 1 Duct-liner Product: 1.5 pounds per cubic foot,2.54 cm thick R-value NRC Parting Strength Layer of Textile Fibers only3.6 0.60 5.0 Uniform layer of Rotary (30%) 3.8 0.60-0.65 4.1 and ofTextile (70%) Fibers

Table 1 shows that a uniform layer of rotary fibers and of textilefibers provides a higher R-value and a higher NRC value than a layer ofonly textile fibers, but with lower tensile strength.

While the present invention has been described with respect to specificembodiments, it is not confined to the specific details set forth, butincludes various changes and modifications that may suggest themselvesto those skilled in the art, all falling within the scope of theinvention as defined by the following claims. The disclosure herein of arange with one or two endpoints is a disclosure of all numbers in therange.

1. A method of making an insulation product, the method comprisingpassing at least one of a first fibrous material and a second fibrousmaterial through a sheet former at a relative humidity of 40% or more toproduce a collection of fibers; and forming the collection of fibersinto a non-woven batt, mat, blanket or board, wherein the first fibrousmaterial contains first fibers each having a diameter in a range of fromgreater than 5 μm to about 16 μm; and the second fibrous materialcontains second fibers each having a diameter in a range of from about 2μm to 5 μm.
 2. The method according to claim 1, wherein the relativehumidity is 50% or more.
 3. The method according to claim 1, furthercomprising adding an antistatic agent to the sheet former while the atleast one of a first fibrous material and a second fibrous materialpasses through the sheet former.
 4. The method according to claim 3,wherein the antistatic agent comprises water.
 5. The method according toclaim 1, wherein the first fibrous material is passed through the sheetformer; and the first fibers are each about 2 cm to about 15 cm long. 6.The method according to claim 1, wherein the second fibrous material ispassed through the sheet former; and the second fibers are each about 1cm to about 5 cm long.
 7. The method according to claim 1, wherein atleast one of the first fibers and the second fibers comprises a glass.8. The method according to claim 1, wherein at least one of the firstfibers and the second fibers comprises a polymer.
 9. The methodaccording to claim 1, wherein the forming comprises adding a binder tothe collection of fibers; and heating the binder to bond the collectionof fibers.
 10. A method of making an insulation product, the methodcomprising adding an antistatic agent to at least one of a first fibrousmaterial and a second fibrous material; passing the antistatic agent andthe at least one of a first fibrous material and a second fibrousmaterial through a sheet former to produce a collection of fibers; andforming the collection of fibers into a non-woven batt, mat, blanket orboard, wherein the first fibrous material contains first fibers eachhaving a diameter in a range of from greater than 5 μm to about 16 μm;and the second fibrous material contains second fibers each having adiameter in a range of from about 2 μm to 5 μm.
 11. The method accordingto claim 10, wherein the relative humidity in the sheet former is 40% ormore.
 12. The method according to claim 10, wherein the antistatic agentcomprises water.
 13. The method according to claim 10, wherein the firstfibrous material is passed through the sheet former; and the firstfibers are each about 2 cm to about 15 cm long.
 14. The method accordingto claim 10, wherein the second fibrous material is passed through thesheet former; and the second fibers are each about 1 cm to about 5 cmlong.
 15. The method according to claim 10 wherein at least one of thefirst fibers and the second fibers comprises a glass.
 16. The methodaccording to claim 10, wherein at least one of the first fibers and thesecond fibers comprises a polymer.
 17. The method according to claim 10,wherein the forming comprises adding a binder that is not the antistaticagent to the collection of fibers; and heating the binder to bond thecollection of fibers.
 18. The method according to claim 10, wherein theantistatic agent comprises a binder; and the forming comprising heatingthe binder to bond the collection of fibers.